While solving important questions for class 10 science chapter 15 – Our Environment, students are required to pay attention dealing with the following topics:
- Why are there components of an ecosystem?
- What is the impact of our activities on the environment?
- Managing our garbage production
- How does the ozone affect ecosystems?
- What can you do to reduce the problem of waste disposal?
Below are some of the important questions for class 10 science chapter 15 – Our Environment from an examination point of view.
Class 10 Science Important Questions Chapter 15 – Our Environment
Q1. Various steps in a food chain represent:
(a) food web
(b) trophic level
(b) trophic level
Q2. With regard to various food chains operating in an ecosystem, man is a:
(c) Producer and consumer
(d) Producer and decomposer
Q3. What is an ecosystem?
An ecosystem is defined as a structural and functional unit of the biosphere. It comprises of living organisms and their non-living environment that interact by means of food chains and biogeo-chemical cycles resulting in energy-flow, biotic diversity and material cycling to form stable self-supporting system.
Q4. List two biotic components of a biosphere.
Two biotic components of a biosphere are:
(i) Producers – Include organisms which can produce their food using simple inorganic compounds, e.g., all green plants, blue green algae (cyanobacteria).
(ii) Consumers – Include organisms which are unable to synthesise their food, therefore, utilise materials and energy stored by the producers or eat other organisms, e.g., all the animals.
Q5. The following organisms form a food chain. Which of these will have the highest concentration of non-biodegradable chemicals? Name the phenomenon associated with it. Insects, Hawk, Grass, Snake, Frog
Among the following organisms of the food chain, hawk being top consumer is present at top most trophic level, hence will have the highest concentration of non-biodegradable chemicals due to a phenomenon known as biomagnification.
Q6. Give an example to illustrate that indiscriminate use of pesticides may result in the degradation of the environment.
Pesticides are the chemicals used to kill plant and animal pests. They are non-biodegradable and toxicants. For example, excessive use of DDT resulted in reduced population of fish eating birds. DDT accumulated in such birds through the food chain. It interfered with the egg shell formation. The shell being thin broke due to weight of the bird during incubation. Hence, their population declined.
Q7. State with reason any two possible consequences of elimination of decomposers from the earth.
Consequences of elimination of decomposers are:
(i) There would be no recycling of nutrients and therefore, raw materials to produce food will not be available to producers. Hence, the food chains will get affected.
(ii) The dead bodies of plants and animals will go on accumulating in the absence of decomposition thereby polluting the environment.
Q8. (a) Create a food chain of the following organisms.
Insect, Hawk, Grass, Snake, Frog
(b) Name the organism at the third trophic level of the created food chain.
(c) Which organism of this food chain will have the highest concentration of non- biodegradable chemicals?
(d) Name the phenomenon associated with it.
(e) If 10,000 Joules of energy is available to frogs, how much energy will be available to snakes in this food chain?
(a) Grass → Insect → Frog → Snake → Hawk
(b) Frog is present in the above created food chain.
(c) Hawk is the top consumer of the food chain, so, it will have high concentration of non- biodegradable chemicals.
(d) Biological magnification
(e) As per 10% law of flow of energy in an ecosystem, only 10% of energy is received by the next trophic level. Hence, in the given food chain, if 10,000 Joules of energy is available to frog, then the energy available to snakes will be 1000 Joule.
Q9. What is a food chain? Why is the flow of energy in an ecosystem unidirectional? Explain briefly.
The sequential interlinking of organisms involving transfer of food energy from the producers, through a series of organisms with repeated eating and being eaten is called the food chain. A food chain involves a nutritive interaction between the living organisms of an ecosystem. There is a unidirectional flow of energy from sun to producers and subsequently to series of different types of consumers, i.e.,
Solar radiations → Producers → Herbivores → Carnivores
It cannot pass in reverse direction. There is always a decrease in the flow of energy and content with rise in trophic level. Large quantity of energy is lost at each step in the form of heat and is also used up in various metabolic activities.
Q10. Why should biodegradable and non- biodegradable wastes be discarded in two separate dustbins?
Biodegradable wastes are decomposed naturally by the action of microbes which degrade them to their simple constituents enabling their nutrients to recycle among the biotic and abiotic components of ecosystem. However, non-biodegradable wastes cannot be disposed off naturally since they cannot be decomposed by microbes. Such wastes are either recycled, incinerated or put in landfills, etc. As the disposal methods of the two types of waste is different, it is advisable to discard the two types of waste in two separate dustbins.